For an online business, a detailed and in depth business plan is usually not necessary unless you are trying to combine your online business with a traditional business. For most online business startups, the detail involved with planning a traditional business is not required. However, it would still be beneficial to you if most of the topics were still covered, even if only briefly. Having a written plan in front of you will help you to focus on important aspects of the business.
The "Accidental Entrepreneur" Plan: Believe it or not, it happens quite often. An impulse, a hobby, or a passing notion turns into a business without warning. One day you're handing your extra back_yard tomatoes or homemade cake to the neighbors, and before you know it you're filling out the forms for a booth at the local farmer's market. Perhaps you create a unique bit of hand_crafted jewelry and wear it to school or work, and then find your phone flooded with messages like, "Where can I get one?" and "I'll pay you to make one for me."